[Hdf-forum] Multiple file opens

[Allen Sanderson]

Hello Elena,

Not a problem to send the stack info. Rarely do I gather this info so  
could you point me to some sample code that will give you the info you  
need.

Cheers,

Allen


Allen Sanderson
SCI Institute
University of Utah
www.sci.utah.edu



On Jan 14, 2010, at 1:13 PM, Elena Pourmal wrote:

> Allen,
>
> Thank you for your report!
> On Jan 14, 2010, at 12:37 PM, Allen Sanderson wrote:
>
>> HI,
>>
>> This morning I was able to track down a bug with a file with  
>> external links where the file was opened twice simultaneously. The  
>> first open was read only. The second open was read write.  However,  
>> if I create the file with the exact same hierarchy but without  
>> links I do not see the bug. I found this odd.
>>
>> Here is the sequence
>>
>> fp1 = open file read only
>>
>> gp1 = open /group using fp1 (note /group is an eternal link)
>>
>> fp2 = open file read/write
>>
>> dp2 = open /group/dataset using fp2
>>
>> the last open fails. I can understand the failure given the gp1 is  
>> read only and dp2 which is under it is trying to perhaps do a write  
>> which could cause some problems.  So it fails.
>>
>> However, if the file has the same hierarchy but without the link it  
>> does not fail. I found this behavior strange as I would have  
>> expected both to behave the same.
>>
>> Obviously, one solution is not to open the file twice which is  
>> certainly possible but also having both opens be read/write also  
>> works. But I am more concerned with the inconsistency.
>>
> yes, good point. Could you please send us an error stack from the  
> failed program?
>
> In our defense :-) RM entry for H5Fopen states "A file can often be  
> opened with a new H5Fopen call without closing an already-open  
> identifier established in a previous H5Fopen or H5Fcreate call. Each  
> such H5Fopen call will return a unique identifier and the file can  
> be accessed through any of these identifiers as long as the  
> identifier remains valid. In such multiply-opened cases, all the  
> open calls should use the same flags argument."
>
> Elena
>
>>
>> Cheers,
>>
>> Allen
>>
>>
>> Allen Sanderson
>> SCI Institute
>> University of Utah
>> www.sci.utah.edu
>>
>>
>>
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>
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